1. Field of the Invention
The present invention relates to a machine for the deposition under a relative vacuum of a material on parts in a loose state.
The invention can be applied to special advantage in the field of deposition under relative vacuum according to the techniques known as PVD (physical vapor deposition) or PACVD (plasma-assisted chemical vapor deposition) and PECVD (plasma-enhanced chemical vapor deposition). These techniques are used to deposit a variety of materials such as metals (aluminum, titanium, copper, gold), carbon, oxides, titanium compounds (carbide, nitride) etc. on practically all supports, especially metals, glass, ceramic as well as plastic materials (ABS, polycarbonate and PMMA).
The fields of application of the invention are very wide-ranging and include the making of decorative layers for spectacles, watches, pens, etc., treatment for tools by the deposition of hard layers on cutting tools or striking tools for example or again certain special applications such as anti-corrosion protective coatings, the manufacture of optical reflectors, etc.
2. Discussion of the Related Art
Whatever the technique used, whether it is PVD, PACVD or PECVD, the known machines for deposition under relative vacuum comprise a chamber in which one or more cathodes are placed, possibly cathode-magnetron devices in PVD, that are negatively polarized with respect to said chamber. Means are also provided for maintaining the chamber under a relative vacuum of one or more gaseous agents. These means generally consist of a vacuum pump used to sweep the chamber with an inflow of gaseous agents coming from any reservoir.
In the case of the PVD technique, said gaseous agents may be a neural gas to which, as needed, there may be added a reactive gas such as oxygen, nitrogen or methane when the material to be deposited is an oxide, nitride or metal carbide, the metal being produced by the spraying of the cathode under the effect of the bombardment of the accelerated ions of neutral gas.
The PACVD or PECVD techniques are implemented by means of gaseous agents that are broken down by a cathode into ion species capable of reacting chemically with the constituent material of the parts to be coated.
It must be noted however that, in known relative vacuum deposition machines such as those mentioned further above, the parts to be treated are generally held mechanically within the chamber by fasteners which, at the end of the treatment, leave a trace on the parts characterized by the absence of deposition at the place where these fasteners have been in contact with the parts.
Even if it is sometimes possible to arrange matters so that the trace is formed at a place that causes no inconvenience to the part considered, a second deposition may prove to be necessary if it is desired to eliminate all traces resulting from the masking of the part by the fastener. This, besides, is not always feasible in view of the conditions of coating.
It may be also be noted that the positioning of the parts one by one by means of fasteners in the treatment chamber takes up a great deal of time and therefore contributes to an increase in the overall cost of the deposition operation. This is especially true when the parts to be coated are, for example, the links of a bracelet that have to be threaded.